Many types of modern communication systems have been developed. One type of communication system that is enjoying increased popularity is wireless radio frequency (RF) communications. Wireless RF communication systems operate by transmitting radio frequency waves between devices. A wireless communication system offers advantages of convenience, a very high degree of mobility, economy (no need for land lines), and long range. Wireless communication systems may include mobile communication devices such as radio communication devices, cellular phones, satellite phones, two-way pagers, personal digital assistants (PDAs), laptop computers with wireless modems, etc.
A wireless communication system may include one or more base stations and one or more mobile communication devices that communicate with each other or with other communication devices via the base stations. A mobile communications device is typically battery powered and includes a transmitter and receiver. The mobile communication devices may move freely while maintaining radio contact with the closest base station. In addition, wireless communication systems may include multiple base stations that are linked together by land lines, such as telephone lines, etc. This allows geographically separated users to communicate by relaying signals between mobile communication devices and between base station communication devices.
FIG. 1 shows a prior art wireless communication system that includes a base station communication device 105 and a mobile communication device 115. The prior art base station 105 includes a carrier wave-based transmitter 106 and a carrier wave-based receiver 107. Likewise, the mobile communication device 115 employs a carrier wave-based transmitter 116 and a carrier wave-based receiver 117. The carrier wave-based transmitters and receivers are devices that employ a modulated RF carrier wave. The modulated RF carrier wave may be used to communicate information between a transmitter and a receiver, including voice and data.
The prior art wireless RF communication system has several drawbacks. In the prior art, one of the largest limitations of a mobile communication device 115 has been the power source, i.e., the battery. Typical batteries do not store enough electrical power to transmit and receive over long periods of time. Therefore, conserving battery power is always a consideration in a mobile communication device 115. This problem is often exacerbated by continuously transmitting a signal, even when data is not being communicated, wasting valuable electrical power.
Another drawback of the prior art is that a carrier wave-based transmitter requires a relatively high power output in order to ensure that the transmitted signal is distinguishable from noise. This is in contrast to a carrier wave-based receiver, which requires only a modest amount of electrical power in order to receive a RF signal and recover any information therein. The relatively large transmit power is not suitable in light of the relatively short battery life of a mobile communication device 115. Therefore, in the prior art mobile communication device 115 the battery must be large and heavy in order to supply the required electrical power.
Yet another drawback is that the mobile communication device 115 of the prior art must supply about the same transmit and receive power as the prior art base station communication device 105.
Therefore, there remains a need in the art for improvements in wireless communication systems.